Rust with AVR support

This project adds support for the AVR microcontroller to Rust.

It uses the AVR-LLVM backend.

Caveats

While the stock libcore may be compiled, certain code patterns may still exercise code in LLVM that is broken or that produces miscompiled code. Looking for existing issues or submitting a new issue is appreciated!

Building and installation

This will compile Rust with AVR support. This will not create a fully-fledged cross-compiler, however, as it does not compile any libraries such as libcore or liblibc. To do this, the --target=avr-unknown-unknown flag must be passed to configure, which is not fully supported yet due to bugs.

First make sure you've installed all dependencies for building, as specified in the main Rust repository here. Then use the following commands:

Unix/Linux/*nix

# Grab the avr-rust sources
git clone https://github.com/avr-rust/rust.git --recursive

# Create a directory to place built files in
mkdir build && cd build

# Generate Makefile using settings suitable for an experimental compiler
../rust/configure \
  --enable-debug \
  --disable-docs \
  --enable-llvm-assertions \
  --enable-debug-assertions \
  --enable-optimize \
  --enable-llvm-release-debuginfo \
  --experimental-targets=AVR \
  --prefix=/opt/avr-rust

# Build the compiler, optionally install it to /opt/avr-rust
make
make install

# Register the toolchain with rustup
rustup toolchain link avr-toolchain $(realpath $(find . -name 'stage2'))

# Optionally enable the avr toolchain globally
rustup default avr-toolchain

Notes for macOS

The conventional install directory for macOS is /usr/local/avr-rust rather than the Linux default /opt/avr-rust, so before the steps below, you must:

1. Edit build/config.toml to set prefix = '/usr/local/avr-rust'.
2. Ensure /usr/local/avr-rust exists and has the correct permissions: sudo mkdir /usr/local/avr-rust && sudo chown ${USER}:admin /usr/local/avr-rust

Finally, realpath isn't included by default on macOS but is included in GNU Coreutils, so you can either brew install coreutils so the rustup toolchain... step works properly, or just use the explicit path (rustup toolchain link avr-toolchain /usr/local/avr-rust).

# Grab the avr-rust sources
git clone https://github.com/avr-rust/rust.git --recursive

# Create a directory to place built files in
mkdir build && cd build

# Generate Makefile using settings suitable for an experimental compiler
../rust/configure \
  --enable-debug \
  --disable-docs \
  --enable-llvm-assertions \
  --enable-debug-assertions \
  --enable-optimize \
  --enable-llvm-release-debuginfo \
  --experimental-targets=AVR \
  --prefix=/usr/local/avr-rust

# Build the compiler, install it to /usr/local/avr-rust
make
make install

# Register the toolchain with rustup
rustup toolchain link avr-toolchain /usr/local/avr-rust

# Optionally enable the avr toolchain globally
rustup default avr-toolchain

Usage

With Xargo (recommended)

Take a look at the example blink program.

Vanilla rustc

AVR support is enabled by passing the --target avr-unknown-unknown flag to rustc.

Note that the Rust libcore library (essentially required for every Rust program), must be manually compiled for it to be used, as it will not be built for AVR during compiler compilation (yet). Work is currently being done in order to allow libcore to be automatically compiled for AVR.